The present invention relates to safety devices, and in particular to a pull-back safety mechanism for presses and other similar machines.
Pull-back safety devices are used in conjunction with riveting, staking, eyeletting, resistance welding, metal forming, and a wide variety of other industrial operations in which stock material is manually inserted between converging machine parts. Such devices typically include tethers attached to the arms or wrists of the operator, and include a feed position wherein the operator is permitted sufficient limb movement to place the stock material between the converging parts, such as between mating die halves when the die is open. When the die halves are converged, the safety device is shifted to a safety position, wherein the hands of the operator, if still positioned between the converging machine parts, are pulled back from inbetween the die halves to prevent them from being injured.
Some pull-back safety devices shift between the feed and safety positions with the motion of the descending die. In this manner, the operator's hands are not completely retracted until the die halves are fully converged. These devices must be carefully adjusted for each individual operator to insure that his hands will not be caught between the die halves, even when the press is operated at maximum production speeds.
Other types of pull-back safety devices employ a reciprocating ram to shift the user's hands between the feed and safety positions. The ram is usually operated by a control circuit which activates the ram and draws the operator's hands back at the beginning of the press stroke. Although such devices retract the operator's hands as the stroke motion begins, if the ram should fail to operate, the hands of the press operator are not retracted.